Initialization

In many situations, we need to initialize the application (i.e perform certain actions) before listening to incoming HTTP requests. This is the case, for example, if you need to establish a connection to the database.

There are two ways to achieve this in FoalTS.

Initializing the Application

The first approach is to add an init method to the root controller class which will be called before the application is fully created. This method can be synchronous or asynchronous.

Example 1

import { dependency } from '@foal/core';

import { ServiceA } from '../services';

export class AppController {

  @dependency
  serviceA: ServiceA;

  async init() {
    await this.serviceA.doSomething();
  }

}

Initializing a Service

The second approach is to add a boot method in your services. This method can be synchronous or asynchronous.

Example

export class ServiceA {

  async boot() {
    await doSomething();
  }

}

Boot methods are executed before AppController.init gets called.

If you manually inject services to your service manager and you want their boot methods to be called, you must specify this in the set method options.

const serviceManager = new ServiceManager();
serviceManager.set(ServiceA, myServiceInstance, { boot: true });

Best Practices

If your initialization consists of several asynchronous tasks, you may want to perform them in parallel. This will reduce the initialization time, which has an impact if you use a serverless architecture.

export class AppController {

  async init() {
    // Don't do
    await createConnection();
    await createAnotherConnection();

    // Do
    await Promise.all([
      createConnection(),
      createAnotherConnection()
    ])
  }

}